A Long Island financial adviser was arrested today for allegedly cheating investors out of hundreds of thousands of dollars during a three-year Ponzi scheme.

Brooklyn federal prosecutors charged Paul Sullivan, 47, of New Hyde Park, LI, with wire fraud after he made a series of financial investments without client authorization that later resulted in substantial trading losses, officials said.

Most of Sullivan’s alleged victims were acquaintances and personal friends who trusted his acumen as a professional stock trader and were devastated when they learned later that their money had vanished, according to several sources involved in the case.

Working with investigators, at least one of the victims discussed the failed investments in a meeting secretly recorded on videotape and Sullivan admitted that what he had done “was completely illegal, completely wrong,” according to a report filed by Brooklyn Assistant US Attorney Daniel Spector.

Peter Tilem, an attorney representing a victim who’s asked to remain anonymous, told The Post that his client had been defrauded out of his “entire life savings.”

After his arrest by Immigration and Customs Enforcement agents, Sullivan was arraigned in Brooklyn federal court and released on $400,000 bail.

Several of those accusing Sullivan of fraud have filed suit against him and last month a Long Island couple, Steven and Shari Nemiroff, secured a civil judgment against the trader in Nassau County Supreme Court for nearly $150,000, court records show.